Velocity selection of double Λ-atoms

Dmitry V. Kosachiov, Yu. Rozhdestvensky

Md. Mabud Hossain, S. Mitra, P Poddar +3 more

Atomic coherence resonances such as electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) signals are observed in a Doppler broadened multi-level system for the D 2 line of 85 Rb atoms in a vapour cell considering different types of atom–laser coupling schemes. Besides the coherence resonances, the nonlinear resonances like velocity selective optical pumping (VSOP) dips and velocity selective resonances (VSR) are also observed for the non-zero velocity selective groups of atoms. In the presence of pump, control and probe laser fields, we observe two EIT signals in a double Λ-type system and two EIA signals in a double V -type system. We are able to see the EIA signal for the non-zero velocity group of atoms when the pump laser is locked with an open transition by a small red detuning. We also report the experimental observation of simultaneous EIT and EIA signals in a (Λ+ V )-type system. The effect of frequency tuning of the control laser is also studied in the presence of the frequency locked pump laser. A simple theoretical analysis explains the experimental results.

Eugeny Korsunsky, Dmitry V. Kosachiov, Yu. Rozhdestvensky +1 more

Sotirios A. Hadjiagapiou

Fam Le Kien, V. I. Balykin

We study laser cooling by velocity-selective coherent population trapping (VSCPT) in a double-Λ scheme with decay beyond the working levels. We show that this additional decay channel filters diffused atoms from trapped ones and provides an ultrasharp atomic momentum distribution.

Vladimir G. Minogin, Gerard Nienhuis

An analytical theory of optical pumping of velocity-selective coherent population trapping states in three-level Λ-atoms is presented. The theory is based on an atomic density matrix in the superpositional state representation. The representation introduced for the atomic density matrix directly describes coherent population trapping (CPT) states in a three-level Λ-atom and yields an approximate analytical description for the shape of the two-peak momentum (velocity) distribution of atoms. Optical pumping of velocity-selective CPT states is described in the superpositional state representation as a process of redistribution of atoms in the region of small velocities due to the photon recoil. Typical times of formation of velocity-selective CPT states are found to be inversely proportional to the square of the recoil energy.